1. Field
The present invention relates to medical devices and, in particular, to catheters provided with electrosurgical devices that can be safely employed as a part of a catheter system that is inserted into a body, for example, catheters having electrosurgical cutting tips that can be safely employed with outer catheters such as bronchoscopes.
2. Background Art
Medicine is providing ever-increasing demands for devices that can navigate narrow passageways to a desired location within a body so that diagnostic and therapeutic procedures can be performed at that location. Currently, elongated medical devices such as catheters can extend into a body from outside via an access point through various connected passageways to a target location. It is sometimes desirable to perform electrosurgical procedures at the target location.
An electrosurgical procedure involves a medical device that uses electrical energy to perform a procedure such as coagulation, dissection, desiccation and cautery. The electrical energy can be provided in either direct current (DC) form or in alternating current (AC) form. However, low frequency electrical energy, including DC, can stimulate muscle and nerves and have potentially undesirable outcomes such as cardiac arrest, if not properly handled. Higher frequency electrical energy, and in particular electrical energy in the radiofrequency (RF) range, may not stimulate muscle or nerves, and therefore may be better suited to core and coagulate tissue.
Modern day elongated medical devices provide the ability for clinicians to navigate to remote and narrow locations within a body. To provide such access, these elongated medical devices must meet a wide variety of requirements such as a desired length and a sufficiently small outer diameter. Further, such a device must also have a sufficiently large inside diameter to permit navigation and delivery of the required functionality to the remote location. In the case of an RF-powered electrosurgical device located at the end of such an elongated medical device, the inside diameter needs to be both sufficiently large to transfer the required energy of the electrosurgical device, as well as provide sufficient diameter consistent with the aspiration requirements of the device. More specifically, sufficient electrical current needs to be delivered to support the RF power level desired at the particular location in the body. For example, an elongated medical device can include an electrosurgical cutting tip for use in a tissue coring procedure. In such an instance, the size of the inner diameter of the elongated medical device should also permit the required aspiration of cored tissue, smoke, blood, and fluid (e.g., bodily fluid) from that location. Further, it is necessary to ensure that the heat generated in the immediate vicinity of the cutting tip be sufficiently isolated from the rest of the elongated medical device so that the elongated medical device does not deteriorate or self-destruct under the resulting thermal conditions.
To guide the electrosurgical device to the target site within a body, the electrosurgical device can be coupled to an elongated delivery device such as an endoscope, for example, a bronchoscope, or other medical device having a lumen, i.e., a catheter. The electrosurgical device can be advanced through the lumen of the elongated delivery device so that the electrosurgical device exits at the target location. However, if the electrosurgical device is energized while within the lumen of the delivery device, the delivery device can be damaged, which can be very costly. To ensure that such damage to the delivery device is not possible, it would be desirable if the electrosurgical device could not be energized until it exits the distal end of the elongated delivery device.